The role of the motility of Methylobacterium in bacterial interactions in drinking water

Bacterial motility is one important factor that affects biofilm formation. In drinking water there are key bacteria in aggregation, whose biology acts to enhance the formation of biofilms. However, it is unclear whether the motility of these key bacteria is an important factor for the interactions between bacteria in drinking water, and, subsequently, in the formation of aggregates, which are precursors to biofilms. Thus, the role of the motility of one of these key bacteria, the Methylobacterium strain DSM 18358, was investigated in the interactions between bacteria in drinking water. The motility of pure Methylobacterium colonies was initially explored; if it was affected by the viscosity of substrate, the temperature, the available energy and the type of substrate. Furthermore, the role of Methylobacterium in the interactions between mixed drinking water bacteria was investigated under the mostly favourable conditions for the motility of Methylobacterium identified before. Overall, the motility of Methylobacterium was found to play a key role in the communication and interactions between bacteria in drinking water. Understanding the role of the motility of key bacteria in drinking water might be useful for the water industry as a potential tool to control the formation of biofilms in drinking water pipes

Nanoparticle transport in saturated porous medium using magnetic resonance imaging

Transport study of nanoparticle (NP) through matrix flow dominated aquifer sand and soils have significant influence in natural systems. To quantify the transport behaviour, magnetic resonance imaging (MRI) was used to image the iron oxide based nanoparticle, Molday ION (carboxyl terminated) through saturated sandstone rock core. T2-weighted images were acquired and the changes in image intensity were calibrated to get a quantitative concentration profiles at various time intervals. These profiles were evaluated through CXTFIT transport model to estimate the transport parameters. These parameters are estimated at various points along the length of the column while classical breakthrough curve analysis cannot provide these details. NP–surface interactions were investigated using DLVO (Derjaguin–Landau–Verwey–Overbeek) theory. The dispersion coefficients (2.55–1.21 × 10−7 m2/s) were found to be decrease with distance, deposition rate constant k (6.70–9.13 × 10−4 (1/s)) and fast deposition rate constant kfast (4.32–8.79 × 10−2 (1/s)) were found to be increase with distance. These parameter variations over length will have a scaling up impact in developing transport models for environmental remediation and risk assessment schemes

Productivity of Florida Springs: Second semi-annual report to the Biology Division, Office of Naval Research progress from February 1, 1953 to June 30, 1953

During this second six months emphasis has been laid on developing a complete understanding of the metabolism of the Silver Springs ecosystem as an example of a community apparently in a steady state. Variation in phosphates, uptake of nitrates, and importance of boron have been estimated. Fluctuation of some major elements has been estimated. Examination of stomach contents has permitted trophic classifications of dominant species and the standing crops have been estimated for these species by number and by dry weight. From these a pyramid of mass has been constructed. Special attention has been paid to bacteria using 3 methods for comparison of Silver Springs with lakes and estimation of the standing crop. The oxygen gradient method has been repeated at half hourly intervals. A carbon-dioxide gradient method has also been used to check the oxygen and to obtain a photosynthetic quotient. Black and light Bell jar experiments have been initiated to obtain checks on the other production measurement and to obtain a community respiration rate. An approximate balance has resulted from estimates of production , respiration , and downstream loss. A flow rate diagram has been constructed to clarify definitions of efficiency and their relationship to a steady state system. Mr. Sloan has statistically verified the increase of insect number and variety away from the boils and demonstrated the reliability of quantitative dipping for aquatic insects. Plans for the third half year include detained and comparative study of the dominant algae and further estimates of rates of growth of all community components. (29pp.

A keystone Methylobacterium strain in biofilm formation in drinking water

The structure of biofilms in drinking water systems is influenced by the interplay between biological and physical processes. Bacterial aggregates in bulk fluid are important in seeding biofilm formation on surfaces. In simple pure and co-cultures, certain bacteria, including Methylobacterium, are implicated in the formation of aggregates. However, it is unclear whether they help to form aggregates in complex mixed bacterial communities. Furthermore, different flow regimes could affect the formation and destination of aggregates. In this study, real drinking water mixed microbial communities were inoculated with the Methylobacterium strain DSM 18358. The propensity of Methylobacterium to promote aggregation was monitored under both stagnant and flow conditions. Under stagnant conditions, Methylobacterium enhanced bacterial aggregation even when it was inoculated in drinking water at 1% relative abundance. Laminar and turbulent flows were developed in a rotating annular reactor. Methylobacterium was found to promote a higher degree of aggregation in turbulent than laminar flow. Finally, fluorescence in situ hybridisation images revealed that Methylobacterium aggregates had distinct spatial structures under the different flow conditions. Overall, Methylobacterium was found to be a key strain in the formation of aggregates in bulk water and subsequently in the formation of biofilms on surfaces

Impact of Methylobacterium in the drinking water microbiome on removal of trihalomethanes

A major class of chlorine disinfection by-products in water treatment and distribution systems is the trihalomethanes. When they occur at high concentration in drinking water they may cause serious problems to human health. Little is known about the capacity of bacterial species that are endemic to drinking water to affect the fate of those chlorination by-products. Methylobacterium species have been previously found to play an important role in the degradation of another major group of chlorine disinfection by-products: the haloacetic acids. Thus, the role that Methylobacterium might play in the concentration of trihalomethanes in drinking water was explored in this study. Concentrations of trihalomethanes were measured in drinking water for different concentrations of Methylobacterium and under different organic matter and chlorine concentrations. The results revealed that when the Methylobacterium DSM 18358 is present in drinking water, even at a low relative abundance of 1%, it plays a key role in decreasing the concentration of trihalomethanes up to 48% from the initial one after 24 hours

The active microbial community more accurately reflects the anaerobic digestion process: 16S rRNA (gene) sequencing as a predictive tool

Background: Amplicon sequencing methods targeting the 16S rRNA gene have been used extensively to investigate microbial community composition and dynamics in anaerobic digestion. These methods successfully characterize amplicons but do not distinguish micro-organisms that are actually responsible for the process. In this research, the archaeal and bacterial community of 48 full-scale anaerobic digestion plants were evaluated on DNA (total community) and RNA (active community) level via 16S rRNA (gene) amplicon sequencing. Results: A significantly higher diversity on DNA compared with the RNA level was observed for archaea, but not for bacteria. Beta diversity analysis showed a significant difference in community composition between the DNA and RNA of both bacteria and archaea. This related with 25.5 and 42.3% of total OTUs for bacteria and archaea, respectively, that showed a significant difference in their DNA and RNA profiles. Similar operational parameters affected the bacterial and archaeal community, yet the differentiating effect between DNA and RNA was much stronger for archaea. Co-occurrence networks and functional prediction profiling confirmed the clear differentiation between DNA and RNA profiles. Conclusions: In conclusion, a clear difference in active (RNA) and total (DNA) community profiles was observed, implying the need for a combined approach to estimate community stability in anaerobic digestion

Productivity of Florida Springs: first semi-annual report to Biology Division, Office of Naval Research, progress from June 1, 1952 to January 31, 1953

Work has begun on studying the factors responsible for productivity in the Florida springs, which are nearly constant temperature, constant chemical, steady state giant laboratories. Progress has been made on five aspects: qualitative description, quantitative description, completion of knowledge of chemical factors, measurement of productivity , development of productivity theory. Measurement of the primary productivity in Silver Springs and Green Cove Springs by two new methods: the raising of organisms in cages, and the measurement of night & day differences in oxygen downstream agree roughly. Production in these springs is greater than previous production figures reported for marine, fresh water, and land areas. Instantaneous measures of production show large variations with season, time of day, cloud cover. Production estimates range from 11,000 lbs per acre per year to 70,000 lbs. glucose per acre per year during daylight hours. Essential stability of the springs environment has been shown with respect to temperature, phosphorus, and plant cover. A correlation of species number with lack of stability has been shown with insects. Quantitative studies have shown very large plant base to pyramids of mass. Correlation of marine invasion with chlorinity has been shown. The essential aspects of pH regulated phosphorus geochemistry in Florida have been outlined. Some theoretical ideas on productivity have been evolved. Mapping of sessile organisms in springs and taxonomic identification of dominants are half completed. Plans for second six months include measurement of herbivore and carnivore production rates and completion of food chain efficiency determinations in Silver Springs as a preparation for subsequent comparisons between springs. (34pp.

Probabilistic models to describe the dynamics of migrating microbial communities

In all but the most sterile environments bacteria will reside in fluid being transported through conduits and some of these will attach and grow as biofilms on the conduit walls. The concentration and diversity of bacteria in the fluid at the point of delivery will be a mix of those when it entered the conduit and those that have become entrained into the flow due to seeding from biofilms. Examples include fluids through conduits such as drinking water pipe networks, endotracheal tubes, catheters and ventilation systems. Here we present two probabilistic models to describe changes in the composition of bulk fluid microbial communities as they are transported through a conduit whilst exposed to biofilm communities. The first (discrete) model simulates absolute numbers of individual cells, whereas the other (continuous) model simulates the relative abundance of taxa in the bulk fluid. The discrete model is founded on a birth-death process whereby the community changes one individual at a time and the numbers of cells in the system can vary. The continuous model is a stochastic differential equation derived from the discrete model and can also accommodate changes in the carrying capacity of the bulk fluid. These models provide a novel Lagrangian framework to investigate and predict the dynamics of migrating microbial communities. In this paper we compare the two models, discuss their merits, possible applications and present simulation results in the context of drinking water distribution systems. Our results provide novel insight into the effects of stochastic dynamics on the composition of non-stationary microbial communities that are exposed to biofilms and provides a new avenue for modelling microbial dynamics in systems where fluids are being transported

Metagenomic sequencing unravels gene fragments with phylogenetic signatures of O2-tolerant NiFe membrane-bound hydrogenases in lacustrine sediment

Many promising hydrogen technologies utilising hydrogenase enzymes have been slowed by the fact that most hydrogenases are extremely sensitive to O2. Within the group 1 membrane-bound NiFe hydrogenase, naturally occurring tolerant enzymes do exist, and O2 tolerance has been largely attributed to changes in iron–sulphur clusters coordinated by different numbers of cysteine residues in the enzyme’s small subunit. Indeed, previous work has provided a robust phylogenetic signature of O2 tolerance [1], which when combined with new sequencing technologies makes bio prospecting in nature a far more viable endeavour. However, making sense of such a vast diversity is still challenging and could be simplified if known species with O2-tolerant enzymes were annotated with information on metabolism and natural environments. Here, we utilised a bioinformatics approach to compare O2-tolerant and sensitive membrane-bound NiFe hydrogenases from 177 bacterial species with fully sequenced genomes for differences in their taxonomy, O2 requirements, and natural environment. Following this, we interrogated a metagenome from lacustrine surface sediment for novel hydrogenases via high-throughput shotgun DNA sequencing using the Illumina™ MiSeq platform. We found 44 new NiFe group 1 membrane-bound hydrogenase sequence fragments, five of which segregated with the tolerant group on the phylogenetic tree of the enzyme’s small subunit, and four with the large subunit, indicating de novo O2-tolerant protein sequences that could help engineer more efficient hydrogenases

Productivity of Florida Springs: First annual (3rd semi-annual) report to Biology Branch, Office of Naval Research progress from January 1 to December 31, 1953

By means of new methods it has been possible to measure the overall community metabolism as well as the standing state community in Silver Springs. Photosynthetic rates have been determined by downstream gradient methods, transplantation growth plots, and bell jars diurnally and annually. Respiration rates have been estimated with bell jars. The downstream losses of particulate, and dissolved organic matter have been found to balance, the excess of photosynthesis over respiration. The community has thus been demonstrated to be in a constant temperature, steady state, somewhat comparable to a climax on land. Nitrate, phosphate, and major chemical constituents are essentially constant. There is an approximate constancy of standing crop of organisms although the production rates in summer are three times those in the winter. Some evidence suggests that there, are photoperiodic changes in reproduction rates in spite of constant temperature. Rates of protein syntehsis estimated from nitrate uptake downstream agree (1) with photosynthetic quotients obtained from carbon dioxide and oxygen uptake downstream and (2) with the nitrogen content of the community. The overall annual production of 50,000 lbs/acre is the greatest productivity we know of on land or sea. Such high figures seem reasonable with the flow of high nutrient, warm water and high light intensity over a dense periphyton community. Theoretical concepts of steady state thermodynamics have been applied to show that self maintaining open systems tend to adjust to high power and low efficiency output. The 3% photosynthetic efficiency observed in Silver Springs is in agreement with this principle. Pyramids of weight and pyramids of number have been determined including bacteria. These pyramids are similar to some in the literature. The contribution of an acre of a fertile stream annually is readily inferred from data obtained on downstream increase of bacteria, chlorophyll, and organic matter. In other springs, Mr. Sloan has related stability of insect populations to chlorinity and to gradients of stability of environmental factors. Dr. L.S. Whitford during the summer made an ecological and taxonomic study of the distribution of algae in 26 contrasting springs. From this lists and from analytical data on the chemostatic water in these springs one can infer culture conditions necessary for many species. (27 pages